Gas lift plunger



April 13, 1954 J. zABA GAS LIFT PLUNGER Filed March 22, 1950 INVEN TOR.

Joseph Zobo Fig. 3

V ATTORNEY Patented Apr. 13, 1954 GAS LIFT PLUNGER Joseph Zaba, Tulsa,Okla., assigner to Stanolind Oil and Gas Company, Tulsa, Okla., acorporationof Delaware Application March 22, 1950, Serial No. 151,139

(Cl. S-52) 6 Claims.

This invention pertains to an apparatus for artificially producingwells. More particularly, this invention pertains-to an improved plungerfor use in gas lifting oil Wells.

In gas lifting liquid from a Well, the common practice has been torinject gas by any of a number of means into anl eduction tube below thelevel of the fluid, thereby raising the liquid level to the surfaceeither by-aeration of the column of liquid in the eduction tubing or bymere displacement of slugs of liquid with thegas. As is well known, byeither method the gas-oil ratio is generally very high; and, therefore,the efficiency of the process is too low to justify gas lift operationsin many wells-particularly stripper or marginal wells.

It has been proposed to improve this eiciency of gas lift by inserting adivider means, suchas a plunger, between the liquid column and the gascolumn which is used to lift the liquid column to the surface. By thismeans 'cy-passing of liquid with the gas is avoided, and the gas-oilratio is substantially reduced. A plunger of `this typeand method ofoperation areshown in U. S. 1,833,778, Fletcher. Althoughvariousmodincations and improvements have been madein` that system ofgas lifting wells, it has not been widely used clue to the highinstallation cost. I have found that in that system the clearancebetween the plunger and the tubing must be very low to prevent the gasfrom by-passing the plunger and that, in order to maintain thisclearancein the proper range, a specially bored or selected tubingstring is required. The cost of special boring is often prohibitive, inthe iirst place; and, second, thepossibility of injury, such as dentingof the tubing string during handling, is rather high. Wells requiringarticial lift generally will not justify such expense and suchl risk.While it would be possible occasionally to select tubing joints having asubstantially uniform diameter, for a special string, obviously, no oilproducer could afford to buy tubing, select joints therefrom, and sellor salvage the remainder of the joints. Even with selected joints,however, the eniciency of a plunger gas lift system using a fixeddiameter plunger is reduced by even minor variations in the insidediameter ofv the tubing. Such variation cannot be avoided inv a longtubing string. Since the fixed diameter plunger must be small enough topass the smallest diameter in the complete tubing string, itinvaria'bly` allowsgas by-passing at the larger points in the string.These-diflicultieshavesubstantially limited the use of the plunger gaslift system.

It.isthereforeanlobject of this invention to provide an. improvedapparatus for gas lifting-wells.

It is a further object of this invention to provide an improved gas liftplunger. A still further obj'ect of this invention is to provide a gaslift plunger which will prevent by-passing of fluid in tubing havingrandom variations in diameter. These and other objects of this inventionwill becomeapparent from the following description o certain embodimentsof my invention which are presented for the purpose of illustration. Inthis description, reference will be made to the accompanying drawings inwhich:

Figure 1 is a View partially in cross-section of a diagrammaticrepresentation of one type of improved gas lift plunger, showing thesealing rings in an expanded or power stroke position;

Figure 2 is a View partially in cross-section of the gas lift plungershown in Figure l, showingthe sealing rings in contracted or returnstroke position;

Figure 3 is a cross-sectional view of an alternative means forcontracting and expanding the sealing ring, the sealing ring being shownin exfpanded position; and

Figure 4 is a cross-sectional view of the apparatus shown in Figure 3,the sealing ring being shown in contracted position.

This invention, in brief, comprises a gas lift, plunger which is adaptedto being reciprocated throughout substantially the whole length of arandom-diameter well tubing string. As the plunger ascends with a loadof liquid, ilexible seal.- ing rings mounted on a body are expandedresiliently against the inner walls of the tubing. When the plungerarrives at the surface with its load of liquid, the sealing rings arecontracted and the plunger is allowed to fall relatively freely throughthe tubing string to a bottom stop (not shown) which is locatedsubstantially below the working fluid level of the well'. Atsubstantially the position of the lower stop in the tubing, the sealingrings are again expanded; and, as gas pressure is applied below theplunger, the plunger is again driven to the surface.

Turning now to a detailed description of the drawings, an embodiment ofmy gas lift plunger is shown in a section of tubing lil. The plungerconsists essentially of a tubular framework or body l l having a fishingneck l2 at the top thereof, a multiplicity of sealing rings i3 disposedalong the body, and a central tripping rod i4. The sealing rings are,preferably, metallic-for example, hardened steel-and will operate forsubstantial periods of time in the tubing without appreciable wear. Thediameter of these rings may-be variedV substantially due to the step outi5, asshown in Figures 1 and 2, without permitting the uid to by-passthe rings. It is desirable, for example, that in operation the diameterof the ring may Vary as much as one-half inch in the 2- or 21/2- inchtubing size ring without permitting fluid to by-pass the sealing ring.In larger tubing sizes the variation is proportionately larger.Furthermore, the ring is preferably highly flexible, so that it may bereadily mounted in the recess or groove it of the body. A number oftapered ribs il may be attached to the inside of the sealing rings sothat when the resilient frustro-conical expanders it, which are attachedto central tripping rod i4, are moved up and down, the sealing ring willbe resiliently expanded and contracted.

The body may be a grooved, tubular member substantially in one piece, asindicated in Figure 1, or it may be made up of a number of sections 2G,as indicated in Figure 2, each section containing a groove for thesealing ring and means to conneet to the sections above and below. Thistype of construction is preferred in seme cases, since it facilitatesassembly of the sealing rings on the body of the gas lift plunger.

These frustro-conical cams or expanders It may be constructed of anyresilient material, such as rubber, preferably synthetic, leaf springslongitudinally mounted on the rod, or the like. As indicated, they havethe small-diameter end at the top and the large-diameter end at thebottom and are mounted along the tripping rod at distances correspondingto the spacing of the sealing rings on body Il. The tripping rod extendsout of both ends of the body for a distance sufficient to provide thenecessary axial movement of the expanders and lateral movement to thesealing ring when the rod is moved. That is, with reference specicallyto Figure l, during the power stroke, the tripping rod extends out ofthe upper end of the body a suflicient distance so that when the upperend of the tripping body strikes the upper stop (not shown) in thetubing, the tripping rod, including the expanders, will be moveddownward in the body, and the sealing ringdiameter will be decreasedfrom about one-eighth to about one-half inch, or more. Similarly, whenthe plunger is on the down stroke, the tripping rod. extends out of thebottom of the body a sufficient distance to return the rod and sealingrings to the expanded position when the rod strikes the lower stop (notshown) in the tubing.

In operation the plunger is placed in the tubing in the position shownin Figure Z-the contracted position. Being substantially smaller thanthe tubing, it falls relatively freely until the lower end of thetripping rod strikes the bottom stop in the tubing. When the trippingrod strikes the bottom stop, due to the inertia of the body, taperedribs Il are forced down over expanders I8, and the sealing rings i4 areforced out against the inner wall of the tubing. Liquid-for exampleoilmay then be allowed to .dow into the tubing above the plunger; or, insome cases, the frequency of oscillations of the plunger in the tubingmay be adjusted so that by the time the plunger reaches the bottomposition sufficient oil has accumulated in the bottom of the tubing tostart another cycle. In any case, when sufhcient oil has accumulated ontop of the plunger, gas is injected into the tubing below the plunger ata pressure sufficient to overcome the friction Vof the sealing rings andthe iiuid head. I have found, for example, that in 21/2-inch tubing apressure of about 70 p. s. i. is required to overcome the static forcedue to 1 barrel of oil in the tubing and that the force required toovercome the friction between the sealing rings and the inner tubingwall varies substantially. Even though the frictional forces do varysubstantially, I have found that a gas pressure of about 200 p. s. i. isadequate in practically all cases when about l barrel of oil is liftedper plunger trip in 21/2-inch tubing.

When sumcient pressure is applied to overcome the static force due tothe head of oil and the friction between the sealing ring and tubing,the plunger moves upward in the tubing until the upper end of thetripping rod strikes the upper stop in the tubing. This stop ispreferably above therow line connection to the tubing, so that al1 ofthe oil carried up by the plunger is discharged into the flow line fromthe well before the tripping rod strikes the upper stop. Obviously,various resilient means may be provided at the upper stop, as Well as atthe lower stop, to decelerate the plunger and prevent injury thereto.When the upper end of the tripping rod strikes the upper stop, theinertia of the plunger body carries the sealing rings and tapered ribsupward relative to the expanders, contracting or decreasing the diameterof the sealing rings. When this diameter is decreased, the fluid willnot support the plunger, so it falls relatively freely through thetubing. As it falls through the tubing, the sealing rings, the trippingrod, and expanders are in the position shown in Figure 2.

In the embodiment of my invention shown in Figures 1 and 2 and describedabove, the sealing ring is installed on the body in a contractedposition; i. e., the ring without the application of an external forceis normally smaller than the tubing in which it is to operate. It isexpanded by the frustro-conical expander as indicated. In some cases Ihave found it desirable to construct the sealing ring so that in itsnormal position the diameter is equal to or greater than the maximuminternal diameter of the tubing in which it is to operate. Thisalternative design is illustrated in Figures 3 and 4. In the expandedposition, as shown in Figure 3, the condition during ascent of theplunger, no external force is applied to the sealing ring; instead, acage 2l, consisting cf a number of tapered levers 22, is attached totripping rod ld. These tapered members are vadapted to contract thediameter ofthe sealing ring when the tripping rod is moved downwardrelative to the sealing ring. That is, the tapered members, by movingdownward relative to the links 2-3 attached to the inner surface of thesealing rings, contract the sealing rings, as shown in Figure 4.

The operation of this embodiment is substantially identical toi theoperation of the embodiment previously described. As in that embodiment,the tripping rod is adapted to extend beyond the ends of the body il andcontact the upper and lower stops to reverse the plunger. When thetripping rod is in the raised position relative to the body, asindicated in Figure 3, the cams or tapered levers 22 are out'of contactwith links 23, and the sealing ring is free to expand or contract withinthe tubing. When the plunger reaches the surface and the tripping rodstrikes the upper stop (not shown), the tripping rod is driven downwardrelative to the body, forcing the tapered levers 22 down into links 23and compressing sealing ring I3 so that the pressure drop across theplunger is decreased, and the plunger falls relatively freely throughthe liquids and/or gases in the tubing. When the plunger reaches thebottom of the tubing, the tripping rod strikes the lower stop, forcingthe tripping rod up rela- I tive to the body and withdrawing the taperedlevers 22 from links 23, thereby allowing the sealing ring to againexpand.

The plunger may be driven to the surface with formation gas or gasinjected into the tubing below the plunger via the annulus between thetubing and casing. Various means have been proposed fo-r timing theinjection of gas. For example, the gas may be injected in time cyclescontrolled by a clock mechanism at the surface; it may be injected byuse of an intermitter valve actuated by liquid head in the tube; it maybe injected by a bottom-hole valve actuated from the surface, or thelike. This invention is therefore not limited by the method or apparatusused to inject gas, to shut off gas, or the like. Furthermore, variousmodifications of auxiliary apparatus proposed in this art, such astubing packers, formation packers, gas-lift valves, and the like, can beapplied to my improved gas lift plunger without departing from thespirit of my invention. The invention should, therefore, not beconstrued to be limited by the above description, which is presentedmerely for the purpose of illustration, but should be construed in lightof the appended claims.

I claim:

1. A plunger having a plurality of hollow cylindrical members eachhaving a vertically disposed annular sidewall and an opening extendingalong the vertical axis thereof, said cylindrical members beingvertically spaced to provide an annular space between adjacentcylindrical members and having the axial openings therein in alignment,a exible metallic split ring member mounted in each annular spacebetween adjacent cylindrical members and adapted for lateral movementinwardly and outwardly with respect to the vertical annular sidewalls ofadjacent cylindrical members, a tripping rod mounted in said cylindricalmembers and extending through the axially aligned openings therein, saidrod being vertically movable with respect to said cylindrical members, aplurality of cam means rigidly mounted on said tripping rod. one of saidcam means being positioned in each annular space between adjacentcylindrical members, and a laterally extending member mounted in eachannular space and engaging each of said split rings and adapted to beengaged by said cam means, said tripping rod and said cam means mountedthereon being movable along the vertical axis of said cylindricalmembers for causing engagement and, in turn, lateral movement of saidlaterally extending members and said split ring member with respect tothe vertical annular sidewalls of adjacent cylindrical members.

2. A plunger as set forth in claim 1 having a pair of vertically spacedcylindrical members providing an annular space between said pair ofcylindrical members, a iiexible metallic split ring member mounted insaid annular space and a cam means rigidly mounted on said tripping rodand positioned in the annular space between said pair of cylindricalmembers.

3. A plunger as set forth in claim 2 in which said cam means is afrustroconical member and the outside diameter of said flexible metallicsplit ring member is normally substantially equal to the diameter ofsaid cylindrical members and wherein said split ring member is expandedbeyond said annular sidewalls of adjacent cylindrical members when saidtripping rod and said cam means are displaced upwardly relative to saidcylindrical members.

4. A plunger for raising liquids on the power stroke from wells with gasunder pressure co-mprising a cylindrical body having a circumferentialgroove on the outer surface, a ilexible metallic sealing ring disposedin said groove and adapted for expansion beyond the periphery of saidcylindrical body, and a longitudinal trip rod including cam meanscoupled to said sealing ring to maintain said sealing ring in acontracted position on the return stroke of said plunger.

5. A plunger for raising liquids through tubing having variable diametercomprising a 'body having circumferential grooves spaced along the outersurface, flexible metallic sealing rings disposed in said grooves andadapted for expansion beyond the periphery of said body, a tripping roddisposed within and movable longitudinally relative to said body andcages containing a multiplicity of cams secured to and spaced along saidtripping rod corresponding to the spacing of said circumferentialgrooves on said body, said cams being operatively connected to saidsealing rings and said cages and said cams being moved by said trippingrod to contract said sealing rings when said cages are displaceddownward relative to said body, whereby said sealing rings in theexpanded position will conform to variations in the diameter of saidtubing, and said sealing rings may be contracted.

`8. A plunger for raising liquids on lthe power stroke from wellsthrough tubing having variable diameter comprising a cylindrical bodylhaving at least one cylindrical groove in the outer surface. a flexiblemetallic sealing ring disposed in said groove and adapted to expandbeyond the periphery of said cylindrical body and to contract as thediameter of said tubing contracts, and cams extending longitudinally ofsaid body and coupled to said sealing ring to contract said sealing ringwhen said cams are moved downward relative to said ring and to maintainsaid sealing ring in a contracted position on the return stroke of saidplunger.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,002,173 Naegelen Aug. 29, 1911 1,776,889 Claytor Sept. 30,1930 1,819,994 Claytor Aug. 18, 1931 2,001,012 Burgher May 14, 19352,018,205 Evans Oct. 22, 1935 2,237,408 Burgher Apr. 8, 1941 FOREIGNPATENTS Number Country Date 645,974 France July 9, 1928

